1. Field of the Invention
This invention relates to an apparatus for forming a nonwoven fibrous web, and more particularly to an apparatus for forming a nonwoven fibrous web from multiple laps of staple fibers.
2. Description of the Prior Art
Nonwoven webs of oriented staple length fibers are well known in the prior art, and have been conventionally formed on carding machines which orient the fibers predominately in the machine-direction of web formation. These webs have excellent machine-directon strength due to the predominate fiber orientation in that direction; however, this strength is obtained at a sacrifice of cross-machine-direction strength.
An improved apparatus for achieving enhanced cross-machine-direction strength in nonwoven fibrous webs formed from multiple laps of predominately machine-direction-oriented staple length fibers is disclosed in U.S. Pat. No. 3,772,107, issued to Gentile et al on Nov. 13, 1973, and assigned to Scott Paper Company. That apparatus includes a plurality of lap-forming means, preferably in the form of carding machines, for forming multiple laps of staple-length fibers and for directing said laps through an enclosed flow path into overlying relationship within a lap-confining channel. The carding machines generate air currents which are directed into the lap-confining channel under substantially laminar air flow conditions to form air barriers between the overlying laps and between the lower lap and the upper run of an air-impervious conveyor belt. The upper run of the conveyor belt is moved in a horizontal path through the lapconfining channel, and then is diverted upwardly at an acute angle to direct the laps into a horizontally disposed fiber spreading and reorienting section. The diversion of the upper run of the conveyor belt from its horizontal path into its upwardly inclined path takes place by directing the upper run around a conveyor diverting roll. The Gentile et al apparatus further includes a calendering section disposed downstream of the fiber spreading and reorienting section for pressing the adjacent overlying laps together to form a unitary nonwoven fibrous web after the fibers in the laps have been spread and reoriented, a bonding section disposed downstream of the calendering section for bonding together the fibers of the unitary nonwoven fibrous web and a drying section for both drying and curing the bonding material to complete the formation of the nonwoven web.
The Gentile et al apparatus was designed to prevent any significant compression of the laps until after the fiber spreading and reorienting operation. In this manner the air barriers formed between the overlying laps of staple fibers were maintained during the fiber spreading and reorienting operation to achieve a greater degree of fiber reorientation and randomization then was achievable when the laps were pressed into a unitary web construction prior to the spreading and reorienting operation. A complete discussion of the advantages of the Gentile et al apparatus is set forth in the U.S. Pat. No. 3,772,107, and for the purpose of brevity will not be repeated herein.
Although the Gentile et al apparatus accomplished its intended objective of forming a nonwoven fibrous web with enhanced cross-machine-direction strength, it has been found that at web forming speeds exceeding about 300 feet per minute (i.e.), the speed of web removal from the drying section) the finished nonwoven fibrous web consistently contained undesirable wrinkles extending in the machine direction of web formation.